Stripping of spent catalyst in hydrocarbon conversion processes



Dec. 14, 1948. D. REAQJR 2,456,148 STRIPPING OF SPENT CATALYST N HYDROCARBON t CONVERSION PROCESSES Filed May 25, 1945 Patented Dec. 14, 1948 IUNITED STATES PATENT OFFICE STRIPPIN G OF SPENT CVATALYST IN HYDRO- CARBON CONVERSION PROCESSES Davis Read, Jr., Downers Grove, Ill., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application Mayv25, 1945, Serial No. 595,715

7 Claims.

, been deactivated by the deposition of carbonaceous materials on the surface prior to the regeneration of the catalyst.

In recent years many catalytic processes have been employed for the conversion of hydrocarbons which utilize catalysts which gradually be- Y come contaminated or deactivated by the deposition of carbonaceous material on the catalyst surfaces. It is the usual procedure to regenerate or reactivate these catalysts by burning o the carbonaceous deposit. However, most of these catalytic substances, either'synthetic or natural, are somewhat thermophobic and excessively high temperatures cause a deterioration of their catalytic activity, thereby shortening the period of useful life. Various regeneration techniques have been developed to prevent excessive temperature during regeneration, the most common being the use of an inert diluent along with the regenerating gas, thereby increasingv the heat capacity of the regenerating medium and providing a means for regulating the temperature rise'. In all of these regeneration operations it is a practice to remove a portion of the residual oil retained on the catalyst by absorption, prior to contacting the catalytic material with the regenerating medium. This removal of residual oil performs two functions, first, it decreases the amount of combustible material entering the reaction zone thereby effecting a corresponding decrease in the amount of regenerating medium required and, secondly,l because of the decreased amount of combustible material present a lower temperature is obtained in the regenerating zone. Further, the residual oils removed from the catalyst prior to regeneration may be recovered instead of being burned in the regeneration zone, thus, improving the economics of the hydrocarbon conversion process.

The methods ordinarily employed in` removing the residual oils from the catalyst usually entail the use of some medium, such as steam, which displaces the oil from the catalyst surface, or the use of some other inert material such as combustion gases which are very low in oxygen concentration. Either of these types of removal have disadvantages inherent in the particular medium employed. `It has been found that the use of steam tends to permanently decrease the catalyst activity making it necessary to change or add fresh catalyst at frequentv intervals to maintain @sa high conversion rate in the operation. Combustion gases have not been found to be particularly effective for the removal of high boiling hydrocarbon oils and can only be used satisfactorily when the materials retained on the catasi: lyst have a relatively low boiling point.

t' converted into motor fuels having high antiknock It is an object of the present invention to provide a means for removing the residual oils retained on the surfaces of the deactivated catalyst prior to regeneration with a medium which will "212 effectively remove these residual oils without causing any deleterious eect on the catalyst activity.

In one embodiment the present invention consists of a process for the removal of residual oils l-f retained on catalyst surfaces prior to regeneration by subjecting the catalyst to contact with. a naphtha fraction under conditions such that a substantial portion of the residual oils are replaced by the naphtha.

The method herein disclosed of removing residual oils from catalyst surfaces may be satisfactorily employed in various hydrocarbon conversion processes, for example catalytic cracking of high boiling oils to form low boiling materials,

catalytic dehydrogenatlon of aliphatic or'cycloparailinic and cycloolenic hydrocarbons, and is particularly useful in operations wherein high boiling oils such as topped crude or gas oils are properties by the catalytic cracking thereof in the presence of solid synthetic or natural catalysts.

The catalysts which may be employed in the process of the present inventiony comprise silica and alumina composites either synthetic or natural, silica-alumina composited vwith one or more of the oxides of boron, magnesium, titanium, thorium, and zirconium. The above catalyst composites are ordinarily employed in catalytic crack- Iing operations. Catalysts which are effective for dehydrogenation may comprise compounds and particularly the oxides of chromium, molybdenum, tungsten and vanadium either alone or in admixture with one another, or solid supporting matelyst to hydrocarbon oil within the' range of about 0.1:1 to 25:1. In dehydrogenation:operations the temperature will be substantiallyf'theisame as that employed in the cracking operation:

However, the pressure in the @dehydrogenation operations, particularly when eiecting the reformation of gasolines or the formation of aromatic hydrocarbons in the presence of hydrogen or hydrogen containingF gases,y will v be.` substantially highenbrdinarilywithinthe rangeo about 200 to 1000 pounds per squareinch or more. In dehydrogenation operations in the absence `of added hydrogen, the pressure will. Varyfrom slightly super-atmospheric -t-o vabout 200 pounds per-square.inchl Y l y The naphtha iractionswhich may be employed to-displace the high boiling.. hydrocarbon oils from the catalyst may consist of naphtha fractions produced in lthe operation or may be obtained `from extraneous sources, such as cracked or straight-run gasolines. Although the exact reason foran improved stripping efliciencyof heavy oils by the use of `naphtha .is not known it is.. reasonableto assume that 'a part oilthis action is-due to the solvent effect :of thenaphtha onthe higher boilingroils which is not present when employing mediums such as steam or vcombustion gases. If desired, .after Athe removal of the-higher boiling oi-ls bythe use of the naphtha, the. naphtha can also beremovedfquite readily by. the .use of combustion-gases, thus, supplying a catalyst `to Vthe regeneration zone which has. a minimum amount of carbonaceous 4material thereon. K

The features of the present invention will be more apparent. .from the 1 following` l.description of rthe .attached `diagranlmaticdrawing which illustrates in conventional .side Ielevation one Atype ofapparatusin which.the ..objects.of the present.

invention. may be accomplished.` However,4 it is not .intendedlthat this description place any undue limitation on thel generallyA broad scope of the invention.

For simplification .the .description of Vthe drawimg is limited to. an operation wherein a topped crude isr catalytically ycracked toA a high voctane gasoline. a v

Referring yto the drawing, -thev hydrocarbon charge, for example a Mid-Continent topped.

fromscrubbenthrough line l containingy valve 8 intdpumpB-which .discharges through line l0 containingv valve Il and..picks vup catalyst'ircm regeneratorY l2 `which ,iiows through vslide.,.valve l3-and line lli .into lineflil.l ."llhecatalystito, oil weight ratio in line I will be dependent upon a number of factors, for example, the temperature desired in reactor l5, the temperature of the catalyst leaving regenerator l2, etc., but will ordinarily be within the range of from approximately 2:1 to 25:1. As shown in the drawing noA prelminaryviheating.is given the charge oil but upon mixing with the hot regenerated catalyst from regenerator l2 in line l0 substantially -.a1l. of the gas oil is vapcrized and the mixture being introduced into reactor I5 consists of a suspension or" iinelydivided catalyst and hydrocarbon vapors. When desired, however, the charge oil may be preheated by well-known ymeans,` not illustrated.

AReactor'l may comprise a large cylindrical Vessel Vpreferably bailied to insure eiective contact `of the catalyst' and the hydrocarbon. The

f oil'V and-'catalyst suspension pass through a dis- 25 to 35 pounds per cu.Y ft. and the density of the the type of catalyst employed andthe average light phase being. approximately 5 pounds per cu.

ft. or slightly more. The densities of these particular phases will be dependent uponthe velocity of the hydrocarbons through the catalyst body,

particle size ofthe catalyst. The velocity of the hydrocarbon througth the catalyst in reactor i5 is such that the catalyst within the reactor is maintainedin suspension and resembles a liquid f in someof its physical properties, attaining a'distinct level in the reactor. The weight hourly space velocity within reactor weight of hydrocarbon per weight of catalyst per hour will vary depending upon the particular` -reactiondesiredfbutwill ordinarily be within the range of about 0.1 to 5 and preierably.0.5 to 2. The catalyst which is to be regenerated is withdrawn from the dense phase in reactor I5 to valve l@ into line l' into stripper I8 wherein it is contacted withanaphtha fraction obtained as heret wherein a substantial portion of the heat .content i. excessive.

inafter set forth which removes substantiallyV all of the lhigh boiling residual oils retained upon the catalyst `prior to regeneration. The excess naph- `tha vapors and residual oils which have been removed from the catalyst are withdrawn from stripper i8. through line I9 containing valve 20 and commingled with reaction products removed from reactor l5 through line 2l rcontaining valve. To insureV 22 and introduced into -fractionator 23. as complete a stripping oi hydrocarbons from the catalyst as possible a stream of substantially.

oxygen-free combustion gases obtained as hereinaiter set forthis introduced into the stripper below `the yinlet line of the ,-naphtha stripping medium. yThese combustion gasesalso pass out through line i9 lcontaining valve 20 into fractionator 23. In many. cases it may not be necessary to employ the auxiliary combustion gas stripping step since the rresidual amount of naphtha is not The stripped catalyst is withdrawn from stripper i8 through control valve 24 into line 25 and picked up by a stream of air introe duced into the system through line 2li containing Valve 21. .This catalyst is carried through line-26 into .regenerator l2 wherein the combustible materialis removed by oxidation. The combustion gases` substantially .free of oxygen are withdrawnV from regenerator l2 through line 28 containing valve 29 through waste heat boiler 30 ofthe combustion gases is removed by indirect i5 measured as g assegna l heat 'exchange with water to form steam which canl be utilized in some other part of the process. The cooled combustion gases leave waste heat boiler 30 through line 3| containing valve 32 and are introduced into scrubber B as hereinbeiore set forth. Any catalyst entrained in these combustion gases are removed in scrubber 6 by the scrubbing action of the gas oil charge. The catalyst free combustion gases leave scrubber 6 through line 33 and a portion thereof is vented to the atmosphere through valve 34; A portion of this combustion gas may be directed through line 35 containing valve 36 into compressor 31 which discharges through line 38, valve 39 'into stripper I8 to be utilized to strip the naphtha retained on the catalyst during the preliminary stripping operation. The gasoline and gas are separated from the reaction products in fractionator 23 and withdrawn overhead through line 4|l containing valve 4I and sent to the usual separating systems in which the gasoline is separated from the gases and collected as a product of the reaction. The light gases containing isoparaflins and olens may be utilized in polymerization or alkylation operations. The naphtha fraction to be employed in the stripping operation is withdrawn as a side cut from fractionator 23 through line 42 containing valve 43 into pump 44 which discharges througth line 45 containing valve 46 into stripper I8. Another fraction comprising hydrocarbons boiling higher than the naphtha fraction may be withdrawn from the lower portion of fractionator 23 through line 41 containing valve 48 and further treated either catalytically or thermally to augment the total product of gasoline hydrocarbons. A minor proportion of the higher boiling hydrocarbons containing catalyst suspended therein is withdrawn from the bottom of fractionator 23 and recycled to reactor I5 through line 49 containing valve 50.

The above description of the drawing has been limited to a process wherein the catalyst is employed in a iiuidized condition in the reaction zone. However, it is not intended that the broad application of the present invention be limited to this type of operation. The method of stripping herein disclosed is equally applicable to operations wherein the catalyst is disposed within the reaction zone in fixed bed relationship to the incoming reactants, or to an operation in which a relatively compact bed of catalyst is passed downwardly through the reaction zone and the hydrocarbon reactants are passed through the reaction zone either concurrently or countercurrently to the moving mass of catalyst.

I claim as my invention:

1. A hydrocarbon conversion process which comprises subjecting a hydrocarbon charge to conversion conditions in the presence of a solid catalyst in a reaction zone; introducing the resultant conversion products into a fractionation zone and therein separating a naphtha fraction; withdrawing contaminated catalyst from the reaction zone and introducing the same into a stripping zone; contacting said naphtha fraction with said -contaminated catalyst in -said stripping zone to displace high boiling hydrocarbons from the contaminated catalyst; passing thus stripped catalyst in countercurrent contact with substani ing from said stripping zone a stripped catalyst stream and a stream comprising naphtha fraction, displaced high boiling hydrocarbons and combustion'gases; introducing the 'last namedT stream into said fractionation zone without pas-` thereof in the presence of an oxygen-containing ga-s; supplying thus regenerated catalyst to said reaction zone; removing substantially oxygenfree combustion gasesk formed in said regenera" tion zone; and sup-plying at least a portion of said last named gases tosaid stripping zone for countercurrent contact with catalyst therein as hereinbefore described.

2. A hydrocarbon conversion proces-s which comprises subjecting a hydrocarbon charge to conversion conditions in the presence of a solid catalyst in a reaction zone; introducing the resultant conversion products into a fractionation zone and therein separating a naphtha fraction; withdrawing contaminated catalyst from the reaction zone and introducing the same into a separate stripping zone; contacting said naphtha fraction with -said contaminated catalyst in said stripping zone to displace high boiling hydrocarbons from the contaminated catalyst; separately withdrawing from said stripping zone the stripped catalyst and the naphtha fraction containing displaced high boiling hydrocarbons; introducing the latter into said fractionation zone without passage thereof through said reaction zone; introducing said stripped catalyst into a regeneration zone and therein removing combustible contaminant-s from the catalyst; and returning resultant regenerated catalyst to said reaction zone.

3. The process of claim 2 further characterized in that said hydrocarbon charge is cracked in the presence of a solid cracking catalyst.

4. The process of claim 2 further characterized in that said hydrocarbon charge is dehydrogenated in the presence of a solid dehydrogenation catalyst.

5. The process of claim 2 further characterized in that -said hydrocarbon charge comprises a straight run gasoline and said gasoline is reformed in the presence of a solid reforming catalyst.

6. The process of claim 2 further characterized in that said hydrocarbon charge comprises ra topped crude and said topped crude is cracked in the presence of a solid cracking catalyst.

7. A hydrocarbon conversion process which comprises subjecting a hydrocarbon charge to conversion conditions in the presence of a solid catalyst in a reaction zone; introducing the resultant conversion products into a fractionating zone and therein separating a naphtha fraction; withdrawing contaminated catalyst from the reaction zone and introducing the same into a separate stripping zone; contacting said naphtha fraction with said contaminated catalyst in said stripping zone to displace high boiling hydrocarbons from the contaminated catalyst; subsequently passing said contaminated catalyst in countercurrent contact with substantially oxygenfree combustion gases in said stripping zone; separately withdrawing from said stripping zone the stripped catalyst and the naphtha fraction containing displaced high boiling hydrocarbons; introducing the latter into said fractionation zone without passage thereof through said reaction zone; introducing said stripped catalyst into a regeneration zone and therein removing cornbustible contaminants from the catalyst; and

7. returning fresultantfegenerated catalyst' Vto!` said reactionfzone.

DAVIS READ, JR,

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